Regulator for a variable delivery hydraulic pump



R. CHANAL Agg. 19, 1969 :461,804 REGULATOR FOR AVAMABLE DELIVERY HYDRAULIC PUMP Filed NOV. 15, 1967 2 Shets-Sheet vl ATTORNEY l R. CHANAL Aug. 19, 1969 REGULATOR FOR A VARIABLE DELVERY HYDRAULIC PUMP 2 Sheets-Sheet 2 Filed Nov. 15,

INVENTOR Maui.,

ATORNEB United States Patent Int. Cl. F04b 49/019, 1/02; F04d 15/00 U.S. Cl. 103-38 Claims ABSTRACT OF THE DISCLOSURE A combination pressure relief valve and load regulator for a hydraulic pump driven by an internal combustion engine and devised to reduce the load on the engine starter motor when starting from cold, comprising a pressure relief valve, manual operating means therefor, a tilting swashplate variable output pump connected directly to the engine, and means consisting of a piston sliding within a sliding sleeve and interconnected thereto by a compressed gas cushion, the piston being so interconnected with the swashplate and acted upon by the pump oil pressure as to gradually increase the pump load on the motor as the circulating oil heats up.

The present invention relates to a regulator for a variable delivery hydraulic pump.

It is known that variable delivery hydraulic pumps e.g. of swashplate type are often fitted on vehicles or public works machines. The latter are generally left out in the open at night, and in winter time they may be diicult to start each morning. Since the pump on such a machine is directly connected to the engine without the interposition of a clutch, it is apparent that the starter provided for the engine has to overcome a heavy load at the critical starting moment, since it must also drive the hydraulic pump. As the circuit oil may be cold and, consequently, very viscous, the pump therefore demands a considerable amount of power from the starter in addition to that required to turn the engine over.

The object of the present invention is to avoid these disadvantages by constructing a regulator which permits controlled reduction (manually or in any other manner) of the delivery of the pump at the moment of starting and which is cut out when the machine is working.

A regulator according to the present invention comprises a pipe which is connected both to an outlet having a non-return valve fed by a low pressure delivery pump of the installation and to a calibrated delivery tube receiving oil under pressure fed by the main pump, this pipe opening at one end into a relief valve closed by a calibrated spring, which valve may be lifted from its seat by a starting lever. At the other end the said pipe opens into a chamber surrounding a transverse shoulder provided Within a fixed cylinder in which a hollow sleeve slides, also provided with a shoulder, in order to define at this point an annular peripheral space, the said sleeve being connected by resilient means to a similarly sliding control rod. This rod is connected to the swashplate of the main pump from which it receives a force tending to displace it in a direction for cancelling the oil delivery of the pump.

According to a preferred embodiment of the invention, the elastic means provided for connecting the sliding sleeve to the control rod consists of a cushion of compressed gas, which is advantageous in that its pressure varies according to the temperature, so that the link has greater flexibility when cold and particularly when starting. Such a device makes it possible to clear the annular Fice space by lifting the relief valve; therefore the sleeve can slide in its recess until it abuts against the shoulder. This results in the swash pump being moved to the position of substantially zero delivery. Then, when the installation has started to run, the relief valve can be released; since the pump output can no longer ow out of this valve, its pressure pushes the sleeve in the direction for increasing the feed, driving the control rod by way of the gaseous cushion which in turn displaces the swashplate towards the position of maximum feed.

At this moment, the flexibility of the gaseous cushion is high since it is at a low temperature and therefore, under low pressure. A rise in the output oil pressure tends to displace the swashplate in the direction to reduce its output. The plate thus moves taking with it the control rod which easily compresses the gas cushion. A reduction of output results so that the power consumed is minimal. When the installation warms up, the power which the engine can deliver increases as it approaches its normal operating temperature. On the pump side, the gas cushion also increases in temperature and therefore increases its pressure. The cushion will therefore resist more strongly any thrust directed so as to reduce oil out-put and therefore the reduction of output will be less than when the oil circuit is cold. This therefore increases the power absorbed from the engine, the maximum power being adjusted to correspond to the maximum temperature reached by the oil circuit. This makes it possible to obtain: (A) Easy starting in cold weather.

(B) A reduction in the risk of stalling the engine when cold, since little power can be derived from it before the oil installation has reached its normal operating temperature.

In addition, the arrangement of the relief valve according to the invention gives a complete cut-off without causing any oscillatory phenomena as soon as the feed pressure reaches a predetermined limit.

The attached drawings, together with the following description, will enable the invention to be more clearly understood.

FIG. 1 is an axial section through a power regulator according to the invention.

FIG. 2 is a schematic elevation showing how the regulator is mounted on the pump.

FIG. 3 is a partial section taken on the line lII-III of FIG. 1.

FIG. 4 is a diagram illustrating the relation between delivery and pressure which is obtained with a variable delivery swash pump fitted with a regulator according to the present invention.

The regulator illustrated in the drawing is connected by a pressure supply tube 1 to the output of a variable delivery swashplate pump. The pump (FIG. 2) comprises the usual pistons 2 and an adjustable swashplate 3, the angle of tilt of which varies between a position of maximum delivery illustrated in full lines in FIG. 2 and a position of zero feed whichis shown schematically by a plane 4 perpendicular to the axis of rotation 5 of the cylinders belonging to the pistons 2.

The pump is designed in such manner that any rise in pressure in the installation causes the platform 3 to swing about its own axis from the position shown in full lines, towards the position including the plane 4.

At its inner end, a connecting rod 6 comprises a ball and socket joint 7 which is articulated to a guide crosshead 8. The latter slides within cylindrical bore 9 which is formed in a lixed sleeve 10. At its opposing end, the sleeve 10 has a co-axial cylindrical bore 11 of larger diameter joined to the bore 9 at the lever of a transverse shoulder 12. A hollow cylindrical bush 13 slides within the sleeve 10 having two outer diameters different at each of its two ends to enable it to slide tightly in both the bores 9 and 11 in the manner of a differential piston. The two parts of different diameters of the sleeve 13 join at the level of a transverse shoulder 14 which defines an annular space 15 opposite the fixed shoulder 12. The sealed sliding of the bush 13 in the sleeve 10, is ensured by ring seals 16 and 17. The end of the bush 13 which is opposed to the crosshead 8 is closed by a perforated base 1S through which a slide rod 19 passes via a sealing gland 2t). The slide rod 19 extends along the axis of the sleeve 13 and one of its ends has a threaded portion 19a which rigidly anchors it in the crosshead 8.

The end of the rod 19 which is within the bush 13 is connected to a sliding piston 21 provided with ring seals 22.

The piston 21 and the sliding bush 13 may both rest against a fixed support washer 23, which is securely anchored on the sleeve by means of a circlip 24.

The free end of the piston 21 is provided with an inflater coupling 25 of known type, which incorporates a non-return valve operating automatically. The intiater 25 comprises a threaded portion 26 which is capable of being connected to a pressure accumulator or an inflating pump to supply compressed gas to the chamber 27 which is defined between the bottom 18 of the bush 13 and the sliding piston 21. Communication between the infiater 2S and the chamber 27 is effected by an oblique perforation 28. For inflation, an inert gas such as nitrogen is used to form a cushion of gas in the chamber 27.

In addition, a thrust ring 29 is slipped on the bottom of the bush 13 and is located within the chamber 27, serving as a support for the front end of the piston 21 -to limit the amount of displacement of the sliding unit 19-21 relatively to the bush 13 in a direction to compress the gas cushion.

The annular space is connected to one of the ends of a fixed pipe 30, the other end of which discharges radially into a chamber 31 which opens in the centre of a fixed annular seat 32 which is co-axial thereto. A facing 33 of a relief valve 34 has a seating 32, a pair of calibrated springs 35 and 36 tending to close the valve 34. The springs are supported on a sliding seat 37 on which may be moved by turning a regulating screw 38 for adjusting the calibration of the valve 34.

A chamber 31 adjoining the seat 32 comprises a perforated base through which a sliding needle 39 tightly passes. The needle can be moved by a control rod 40 under the action of a manually controlled rocker lever 41 (FIG. 3). The sealing of the needle 39 is effected by a ring seal 42, whilst another ring seal 43 surrounds the* rod 40.

The lever 41 swings about a fixed axis 44, and the end which then extends from the regulator is protected by a bellows 45. The lever 41 is operated by pulling a cable with which its free end is provided in the direction of the arrow 46 (FIG. 3).

The pipe 3i) is connected to a filling aperture 47 connected to a conventional delivery pump (not shown), and it is also connected to the tube 1 which receives oil under pressure from tbe output of the pump. The oil from the tube 1 flows through a calibrated constriction nozzle 48 before reaching the pipe 30.

The oil fed by the delivery pump to the output 47 in the direction of the arrow 49 can reach the pipe 30 only if it is at a sufficient pressure to lift the ball 51 of a nonreturn valve from the seat 5t) against the action of a return spring 52.

The operation of the regulator is as follows:

When the user is ready to start the prime mover of the appliance on which the hydraulic pump is mounted and fitted with a regulator according to the invention, he pulls in the direction of the arrow 46 on the cable 53 with which the' lever 41 is provided, to drive in the rod 40 and thus raise the valve 33 from its seat 32. In these conditions, oil from the delivery pump through the valve 50-51, will escape to the oil sump by the leak past the valve 33. This prevents the pressure rising in the annular space 15, as long as a traction is exerted on the cable 53.

The slide rod 19 and the connecting rod 6 arel linked to the inclined platform 3, whilst they are inter-connected with the bush 13 by the gas cushion in the chamber 27. Under the reaction of the pistons 2 of the swash pump, the platform 3 tends to turn automatically towards the direction of zero feed which corresponds to the transverse plane 4 (FIG. 2). The plate 3 therefore turns to its zero feed position and the pump operates at a condition corresponding to the start 0 of the pressure feed diagram shown in FIG. 4. The prime mover can then start under best conditions, since the jump does not take any power from the starter.

Once the engine has started, the user releases the cable 53. The leak through valve 33 ceases and, consequently the delivery pressure of oil in the pipe 30 reaches chamber 15. The slide bush 13 is pushed to the right, in the direction shown in FIG. l by the arrow 54 and it cariies with it the rod 19 and the connecting rod 6 by means of the' gas cushion in the chamber 27. The plate 3 is thus tilted to a working position. This first phase is shown at point a in the diagram, FIG. 4.

When the pump`begins to feed, it discharges into the tube 1 and consequently into the pipe 30 and into the space 15 where the pressure established is determined by the calibration of the springs 34 and 36 of the valve 33. The point b of FIG. 4 is then reached, after a slight increase in the constant feed delivery pressure.

At the same rate as the delivery pressure increases, the reaction of the pistons 2 on the adjustable platform 3 increases so that the connecting rod 6, the slide* rod 19 and the piston 21 are drawn to the left in the direction indicated in FIG. l by the arrow 55. The result is a cornpression of the gas cushion in the chamber 27 until the piston 21 comes into contact with the thrust ring 29. During this phase, the point of equilibrium corresponding to instantaneous operation of the pump is somewhere on the curve b-c (FIG. 4) which is an arc of a rectangular hyperbola.

If finally the delivery pressure exceeds the selected limit set by the calibration of the springs 34 and 36, the relief valve 33 is raised from its seat 32 and a by-pass is established which is shown in the diagram shown in FIG. 4 as a drop in the afore-mentioned constant pressure feed.

The by-pass leakage permitted by the valve 33 has the effect of causing a drop in the pressure in the annular chamber 15 which at this moment decreases in length until the shoulder 14 comes into contact with the shoulder 12. This results in a displacement of the unit 21-196 in the direction of the arrow 55 and returns the swashplate towards the position of the plane 4. During this movement the balance of the forces developed in the direction of the arrow 55 and in the opposite direction as a result of the reaction of the gas cushion is re-established, so that the piston 21 is slightly withdrawn into the bore 11: this is without effect, however, since it is the reaction of the pistons 2 on the plate 3 which over-rides, and keeps the latter in the position of the plane 4. In this manner the gas cushion returns to its nominal inflation pressure.

It is important to observe that the apparatus of the present invention makes it possible to locate the zone of operation of the pump in an arc b-c which corresponds to starting from cold, this arc being progressively displaced as far as arc b-c of another hyperbola as soon as the engine and the pump have reached their normal operating temperature. Again, when starting from cold, the gas which lls the chamber 27 is at a relatively reduced pressure, so that the elastic reaction of the gas cushion is less when cold than when hot, all other things being equal.

It is known that the power consumed by a pump is determinable from the area located between its regulation curve and the axes OP-OQ. It will be seen in FIG. 4 that this hatched area is smaller at starting (regulation curve b-c) than when in permanent operation (curve bc'). This results in automatic operation of the regulator which compels the pump to operate at full power only when the engine is capable of exerting its maximum power, once its operating temperature is reached.

We claim:

1. A variable output hydraulic pump and a power regulator therefore, comprising: a chamber, a pump supplying low pressure uid to the chamber through a nonreturn valve, the pump also supplying fluid under pressure' to the chamber through a calibrated delivery tube, the calibrated normally closed relief valve connected to the chamber, a control cylinder with a sleeve slidable therein defining an annular chamber which is operatively connected to the chamber, a control rod operatively connected at one end to the sleeve by a resilient chamber, the other end of the rod being connected to the output adjusting means of the pump so as to increase the output of said pump when said sleeve is moved by the pressure of the uid in said annular chamber and by a decrease in the resiliency of the resilient chamber.

2. A power regulator as recited in claim 1, in which said resilient chamber comprises a gas cushion located in a variable volume chamber defined between a piston connected to said control rod and said sliding sleeve, said piston sliding within said sleeve.

3. A power regulator as recited in claim 2, comprising a thrust ring within said sliding sleeve which limits the extent of displacement of said control rod relative to said sleeve, in the direction of compression of said gas cushion.

4. A power regulator as recited in claim 1, including a sliding needle actuated manually by a lever to raise said relief valve from its seating at the moment of starting.

5. A power regulator as recited in claim 1 including an adjusting screw acting on the calibration spring of said calibrated relief valve.

References Cited UNITED STATES PATENTS 1,947,540 2/ 1934 Wallace 103-38 2,129,823 9/1938 Dunn 103--162 2,161,743 6/ 1939 Heinrich et al. 92-1 2,163,479 6/1939 Boddy 103-38 2,417,474 3/ 1947 Feroy 103--38 2,546,571 3/ 1951 Watson 92-1 3,254,604 6/ 1966 Faisandish 103-37 3,256,183() 6/1966 Budzich 103-162 X FOREIGN PATENTS 500,937 2/ 1939 Great Britain.

WILLIAM L. FREEH, Primary Examiner U.S. Cl. X.R. 92--13 103-162 

